The present invention relates to a vehicular headlamp in which a reflector, an electric discharge lamp and a casing containing a lighting circuit board for the electric discharge lamp are mounted within a lamp housing, in which, in the event the container casing is damaged such as in a collision, secondary problems such as fire and electric shock are prevented.
Recently, small-size metal halide lamps have been used as a light source for a vehicular headlamp, instead of the conventional halogen lamps.
FIG. 3 shows an example of a headlamp a employing a metal halide lamp in which a front opening of a reflector c mounted in a lamp housing b is covered by a lens d. The light-emitting portion f of the metal halide lamp e is inserted into a chamber defined by the reflector c and the lens d through an insertion hole g formed through the reflector c. A headlamp unit h is constituted by the reflector c, the lens d and the metal halide lamp e.
A lighting circuit board for the metal halide lamp e is contained in a container casing i. The container casing i, which has a generally rectangular parallelepiped shape, is mounted within the lamp housing b, disposed in a recumbent posture below the reflector c. An activating circuit for producing activating pulses of high voltage for starting the metal halide lamp e and a lighting control circuit are included in the lighting circuit.
In the above lamp, however, if the container casing i is damaged by an impact produced in the event of a collision or the like, there arises a problem that fire, electric shock or the like may occur.
More specifically, when an external force is applied to the lamp in the direction of an arrow A (FIG. 3) in the event of a collision or the like, the container casing i can be crushed between the car body j and a collision object, as shown by a broken line, so that the lighting circuit within the container casing i is damaged, while the high voltage activating pulses continue to be produced. This is very dangerous.